limited slip in a stock 12 bolt rear end

[michael bustamante]

Can Anyone guide me in converting my open 12 bolt 3:73 from my 67 2wd to a limited slip? Is there a rearend from another veh. That i can use the limited slip mechanism from?

[Tropical Snowstorm]

The truck and car 12 bolts were totally different, the cars have a round diff cover and the trucks the oblong shape you'll see under yours. So you'll need to source one for a truck, not a car. You can search around for an original no-slip differential and swap it into yours or an entire housing swap might be easier.

If you pull the chunk out (ring gear and diff) to put in a posi unit you'll probably open a can of worms. Reshimming the backlash and pinion to ring gear depth with a different (either new or used) is a pretty precise operation. Not impossible but a pretty major task.

[cdowns]

drive it into a shop drop it off with the thousand or so dollars and pick it up and drive it home in a few days is the simple foolsproof way to do it

[michael bustamante]

Cdowns. Funny $$$$$
Ill have to look and find a truck 12 bolt setup then. Ive never swapped internals before

[Tropical Snowstorm]

Originally Posted by cdowns

drive it into a shop drop it off with the thousand or so dollars and pick it up and drive it home in a few days is the simple foolsproof way to do it

Yep, typical 4x4 shop is a good place to try. They'll have a differential tech most likely since the off road guys need locker and gear updates when they get going. My last gear and posi swap was with a 2006 Sierra, went from open 3.08 to Trutrac and 3.73s, set me back $800 total. I "know how" and have done it in the past but it's worth it paying someone else to smell like diff fluid and fight the shims, backlash, and weight of the center section in and out.

[bonnieclyde100]

here is an option you wont have to remove ring and pinion or reset the axle shims. just replace your spider gears for this unit. http://www.summitracing.com/parts/pw...3005/overview/

[67chevy1series]

If you want to keep your 3.73 gearing and your gears are fine then all you need to do is get a 4 series posi carrier, new gear oil+limited slip additive, and new gasket and your set.

Pull the diff cover, pull the bolt out that locks the pin through your open carrier then press the axle shaft as far as you can inwards towards the center of the vehicle, pull the c clips out (if they didn't fall out already), pull the axle shafts out or out far enough so they are not in the carrier, undo side bearing caps, pull open carrier out of your housing, in bolt the ring gear from your open carrier and bolt it onto your posi carrier, (best to make your ring gear warm and the posi carrier colder then the ring gear so it slides over nicer) tourque down the ring gear bolts to specified torque, install new side bearings if needed to posi carrier, install posi carrier with the original side shims used with your open carrier (be sure to put the one that was on the left back to the left side and right one back to the right side) reinstall bearing caps and torque bolts to specified torque, then slide your axle shafts in as far as you can again (must take the pin out if the posi carrier) reinstall the c clips and slide axle shafts out as far as you can, install the pin into the posi carrier and torque down the bolt that secures it to specified torque, then you can check your back lash and how the teeth mesh together with gear marking compound if it's within specs then your ready to bolt the diff cover on with new sealant or gasket and fill with right amount gear oil and limited slip additive. Your rear tires must be the exact same size and have same amount of wear of tread, if they are off in size in any way from each other you will cause a lot of stress on the clutch packs!

[Fitz]

Originally Posted by 67chevy1series

If you want to keep your 3.73 gearing and your gears are fine then all you need to do is get a 4 series posi carrier, new gear oil+limited slip additive, and new gasket and your set.

Pull the diff cover, pull the bolt out that locks the pin through your open carrier then press the axle shaft as far as you can inwards towards the center of the vehicle, pull the c clips out (if they didn't fall out already), pull the axle shafts out or out far enough so they are not in the carrier, undo side bearing caps, pull open carrier out of your housing, in bolt the ring gear from your open carrier and bolt it onto your posi carrier, (best to make your ring gear warm and the posi carrier colder then the ring gear so it slides over nicer) tourque down the ring gear bolts to specified torque, install new side bearings if needed to posi carrier, install posi carrier with the original side shims used with your open carrier (be sure to put the one that was on the left back to the left side and right one back to the right side) reinstall bearing caps and torque bolts to specified torque, then slide your axle shafts in as far as you can again (must take the pin out if the posi carrier) reinstall the c clips and slide axle shafts out as far as you can, install the pin into the posi carrier and torque down the bolt that secures it to specified torque, then you can check your back lash and how the teeth mesh together with gear marking compound if it's within specs then your ready to bolt the diff cover on with new sealant or gasket and fill with right amount gear oil and limited slip additive. Your rear tires must be the exact same size and have same amount of wear of tread, if they are off in size in any way from each other you will cause a lot of stress on the clutch packs!

After you have done the above do a "pattern check" using colored grease or just some child's oil paint. Pinion depth is the distance along a ring gear tooth that the pinion gear contacts the face of the tooth. Backlash is revealed by the depth of the pinion gear "wipe" shows from the edge to the root of the ring gear tooth. This one is critical. Too little and the ring gear teeth break off near the edge under acceleration. Too much and both gears will eventually fail. In the photo, the vertical arrow is pinion depth and the horizontal arrow shows backlash. The "wipe" of the pinion gear tooth stays completely on the ring gear tooth in both directions so it is OK.

[Already Gone]

Originally Posted by cdowns

drive it into a shop drop it off with the thousand or so dollars and pick it up and drive it home in a few days is the simple foolsproof way to do it

This is one thing i let the pros play with !!!!

[Fitz]

Originally Posted by Already Gone

This is one thing i let the pros play with !!!!

Rebuilding a diff is much simpler than rebuilding an engine, yet it is the one part of these trucks that is treated as though you must be an expert at witchcraft, arcane black magic or voodoo to even touch one. It has 2 carrier bearings, a center carrier with a ring gear bolted to it and the bearings pressed on the ends of the carrier and a pinion gear with a pressed on bearing. Left side and right side shims to set the backlash and pinion shims to set pinion depth and the pinion nut to preload the pinion bearing. That's it. No more.

That's not complicated. If you can read the overhaul manual and use a dial indicator rebuilding one is easier than installing a new water pump. It took me 30 minutes to tear mine down, replace the open carrier with an Eaton Posi unit and switch the gearset from 3.73 to 4.10 and reassemble it. That diff now has 10,000 miles on it without a whine or whimper. Total parts cost for all new pieces except the pinion nut and the carrier bearing caps was $700.00. Western gear wanted $1400.00 to do the same but I had to accept the "parts they preferred" not the premium pieces I used. Tucson Differential was $1500.00 and the owner told me if he had to use the Richmond Gear gearset and Eaton center section I wanted the cost would be over $2000.00

So I spent the $700.00 kept a minimium of $700.00 more in my checking account and got the parts I wanted instead of the "made in China" stuff they usually use.

[hdff]

Originally Posted by Fitz

Rebuilding a diff is much simpler than rebuilding an engine, yet it is the one part of these trucks that is treated as though you must be an expert at witchcraft, arcane black magic or voodoo to even touch one. It has 2 carrier bearings, a center carrier with a ring gear bolted to it and the bearings pressed on the ends of the carrier and a pinion gear with a pressed on bearing. Left side and right side shims to set the backlash and pinion shims to set pinion depth and the pinion nut to preload the pinion bearing. That's it. No more.

That's not complicated. If you can read the overhaul manual and use a dial indicator rebuilding one is easier than installing a new water pump. It took me 30 minutes to tear mine down, replace the open carrier with an Eaton Posi unit and switch the gearset from 3.73 to 4.10 and reassemble it. That diff now has 10,000 miles on it without a whine or whimper. Total parts cost for all new pieces except the pinion nut and the carrier bearing caps was $700.00. Western gear wanted $1400.00 to do the same but I had to accept the "parts they preferred" not the premium pieces I used. Tucson Differential was $1500.00 and the owner told me if he had to use the Richmond Gear gearset and Eaton center section I wanted the cost would be over $2000.00

So I spent the $700.00 kept a minimium of $700.00 more in my checking account and got the parts I wanted instead of the "made in China" stuff they usually use.

do you like the 4.11 better than the 3.73? mine is fixing to go in for some rear end work and i think i have a 3.07 behind my 402 now. going to put in a posi and change the gear to either a 3.73 or a 4.11, still up in the air about it.

[mechanicalman]

Originally Posted by fitz

rebuilding a diff is much simpler than rebuilding an engine, yet it is the one part of these trucks that is treated as though you must be an expert at witchcraft, arcane black magic or voodoo to even touch one. It has 2 carrier bearings, a center carrier with a ring gear bolted to it and the bearings pressed on the ends of the carrier and a pinion gear with a pressed on bearing. Left side and right side shims to set the backlash and pinion shims to set pinion depth and the pinion nut to preload the pinion bearing. That's it. No more.

That's not complicated. If you can read the overhaul manual and use a dial indicator rebuilding one is easier than installing a new water pump. It took me 30 minutes to tear mine down, replace the open carrier with an eaton posi unit and switch the gearset from 3.73 to 4.10 and reassemble it. That diff now has 10,000 miles on it without a whine or whimper. Total parts cost for all new pieces except the pinion nut and the carrier bearing caps was $700.00. Western gear wanted $1400.00 to do the same but i had to accept the "parts they preferred" not the premium pieces i used. Tucson differential was $1500.00 and the owner told me if he had to use the richmond gear gearset and eaton center section i wanted the cost would be over $2000.00

so i spent the $700.00 kept a minimium of $700.00 more in my checking account and got the parts i wanted instead of the "made in china" stuff they usually use.

x2

[mechanicalman]

Originally Posted by michael bustamante

Can Anyone guide me in converting my open 12 bolt 3:73 from my 67 2wd to a limited slip? Is there a rearend from another veh. That i can use the limited slip mechanism from?

Get one of these
http://www.summitracing.com/parts/dtl-913a315/overview/

Follow Fitz's instructions. If your gears run quiet now, and you duplicate your backlash measurement (provided it's within .005-.012") as it is now and get a good pattern, this will be a piece of CAKE.

Pull a pattern BEFORE you remove the old carrier; this will give you an idea if you need to make an adjustment on the first install. You won't even need to pull the pinion, but a good time to check pinion bearing pre-load while the carrier is OUT. If it needs tightened, use an impact gun on the nut until you get a little drag. Then if you want to put a new seal on the pinion, mark the nut where it aligns with the pinion shaft with a chisel, replace the seal and simply tighten the pinion nut back to the mark.

Installing new side bearings and using the old shims you will likely hit the mark the first time and also have good pre-load but you still might have to play with shims some if your backlash was out to lunch or pinion depth off.

Like I said, if it's set up right now, it's real easy to duplicate.

If you can turn the wrenches, we can supply the experience.

[colgad]

Originally Posted by bonnieclyde100

here is an option you wont have to remove ring and pinion or reset the axle shims. just replace your spider gears for this unit. http://www.summitracing.com/parts/pw...3005/overview/

I never knew this was available!! Great product, thanks for sharing.

[mechanicalman]

Originally Posted by colgad

I never knew this was available!! Great product, thanks for sharing.

I think this is more for a pro street or drag racing setup. Read the review, guy said it's noisy and from what I see I believe him. AND it's more expensive than the trutrac.

[mechanicalman]

Originally Posted by Fitz

Rebuilding a diff is much simpler than rebuilding an engine, yet it is the one part of these trucks that is treated as though you must be an expert at witchcraft, arcane black magic or voodoo to even touch one. It has 2 carrier bearings, a center carrier with a ring gear bolted to it and the bearings pressed on the ends of the carrier and a pinion gear with a pressed on bearing. Left side and right side shims to set the backlash and pinion shims to set pinion depth and the pinion nut to preload the pinion bearing. That's it. No more.

That's not complicated. If you can read the overhaul manual and use a dial indicator rebuilding one is easier than installing a new water pump. It took me 30 minutes to tear mine down, replace the open carrier with an Eaton Posi unit and switch the gearset from 3.73 to 4.10 and reassemble it. That diff now has 10,000 miles on it without a whine or whimper. Total parts cost for all new pieces except the pinion nut and the carrier bearing caps was $700.00

I'm disappointed in you, I thought you were a nice guy.

You left out the ONE BIG STEP that will spell doom on setting up a diff.

Always, after you tighten the last bolt and fill it with oil, you must say "ooga booga wooga mooga" or the diff will die, each and every time. Shame on you!

Ask me how I know LOL

[Fitz]

Originally Posted by hdff

do you like the 4.11 better than the 3.73? mine is fixing to go in for some rear end work and i think i have a 3.07 behind my 402 now. going to put in a posi and change the gear to either a 3.73 or a 4.11, still up in the air about it.

Yes, I like the 4.11 better than the 3.73.....because the truck has a gear vendors 0.7:1 overdrive behind it's turbo 400 trans.

With no overdrive and a 3.73 gearset the engine is at 3200 RPM @ 70 MPH.

With the overdrive and 4.11 gearset I'm turning 2378 RPM at 70 MPH.

This gives the launch and high acceleration of the 4.11 in first and second yet it acts like a 2.73 in overdrive. This combo is the best of both worlds for me.

[Fitz]

Originally Posted by mechanicalman

Get one of these
http://www.summitracing.com/parts/dtl-913a315/overview/

Follow Fitz's instructions. If your gears run quiet now, and you duplicate your backlash measurement (provided it's within .005-.012") as it is now and get a good pattern, this will be a piece of CAKE.

Pull a pattern BEFORE you remove the old carrier; this will give you an idea if you need to make an adjustment on the first install. You won't even need to pull the pinion, but a good time to check pinion bearing pre-load while the carrier is OUT. If it needs tightened, use an impact gun on the nut until you get a little drag. Then if you want to put a new seal on the pinion, mark the nut where it aligns with the pinion shaft with a chisel, replace the seal and simply tighten the pinion nut back to the mark.

Installing new side bearings and using the old shims you will likely hit the mark the first time and also have good pre-load but you still might have to play with shims some if your backlash was out to lunch or pinion depth off.

Like I said, if it's set up right now, it's real easy to duplicate.

If you can turn the wrenches, we can supply the experience.

This is a very good idea! Measuring the pattern BEFORE dismantling that diff will tell you exactly what you want the new gear pattern to look like.

Way to go, Mechanicalman!

[Fitz]

Originally Posted by mechanicalman

I'm disappointed in you, I thought you were a nice guy.

You left out the ONE BIG STEP that will spell doom on setting up a diff.

Always, after you tighten the last bolt and fill it with oil, you must say "ooga booga wooga mooga" or the diff will die, each and every time. Shame on you!

Ask me how I know LOL

I usually say Ugga Bugga Choo Choo while shaking a gourd rattle over the reassembled diff but that's just a matter of taste. The real magic is in that posi oil additive and the gear oil but, as you say, it's THE ONE BIG STEP!

[hdff]

Originally Posted by Fitz

Yes, I like the 4.11 better than the 3.73.....because the truck has a gear vendors 0.7:1 overdrive behind it's turbo 400 trans.

With no overdrive and a 3.73 gearset the engine is at 3200 RPM @ 70 MPH.

With the overdrive and 4.11 gearset I'm turning 2378 RPM at 70 MPH.

This gives the launch and high acceleration of the 4.11 in first and second yet it acts like a 2.73 in overdrive. This combo is the best of both worlds for me.

Forgot to mention that I have a 700r4 behind the 402. So maybe the 4.11 would be good for me also.....

[Fitz]

Originally Posted by hdff

Forgot to mention that I have a 700r4 behind the 402. So maybe the 4.11 would be good for me also.....

Tires make a difference, but with 31 in tall rear tires and a 4.11 diff your 700R4 will give you 2250 RPM at 70 MPH. That's not bad!

[johnw893]

i would bother trying to find a unit from another axle to put in your alot better off spending the 600 on a brand new unit than get one thats going to be worn and who knows its history

[Kennuck]

I've regeared many axles back in my rockcrawlin days. The hardest part of setting up axle gears is getting the pinion depth correct. This has to be set correctly before any side bearing shimming can be done. Since you will be using your original gears the pinion depth is already set so you just have to change the carrier and check your pattern, if any adjustment is needed it will only be side bearing shims.

The trick to setting up axles easily is to buy another set of bearing and grind the I.D. out a couple thousands then you can remove the bearings easily to do shim changes. Once you get the shims right press on new bearings with the shims and your good to go.